Evaluation of physiologic changes in the trauma patient depends greatly upon intrusive techniques such as chronically placed catheters, magnetic flow probes, radioisotope injection and dye dilution methods. Considerable attention has been given to impedance methods for non-invasive clinical determination of cardiac output, peripheral vascular changes, and pulmonary edema. However little work has been done to translate commercially-used nuclear magnetic resonance (NMR) flowmeter principles to biological systems. This study is directed to design cylindrical NMR systems for long term non-invasive monitoring of blood flow in the arm or leg of the trauma patient. Similar systems will be investigated for monitoring abdomen-thoracic flow. Theoretical calculations predict that search coil devices can be designed to measure aortic, vena cava, and perhaps organ flow. These systems will be evaluated in animals, human volunteers and adapted for on-line computer monitoring of physiologic changes in the trauma patient.